ZBuffer problem with rtt [SOLVED]

[tom_gamer]

Hello,

I got a zbuffer problem with real time textures.

Setting:
-irrlicht 1.8
-OpenGL
-drawing objects with my own shader
-shader based on EMT_TRANSPARENT_ALPHA_CHANNEL
-set in all materials the flags for EMF_ZWRITE_ENABLE and EMF_ZBUFFER
-did a 'smgr->getParameters()->setAttribute(scene::ALLOW_ZWRITE_ON_TRANSPARENT, true);'
--> everything works fine, when i draw to the frame buffer


but now i want to do i bit post processing and write the scene to a rtt:

Code: Select all

 
    screenQuad = new CScreenQuadSceneNode(smgr->getRootSceneNode(),smgr,-1);
    rtt = driver->addRenderTargetTexture(dimension2d<u32>(2048, 1024), "RTT0", ECF_A8R8G8B8);
    screenQuad->getMaterial(0).setTexture(0,rtt);
    screenQuad->getMaterial(0).MaterialType = (E_MATERIAL_TYPE)EMT_SOLID;
 

...

Code: Select all

 
    driver->beginScene(true, true, backgroundColor);
 
    driver->setRenderTarget(rtt, true, true, SColor(0,0,0,255));
    smgr->drawAll();
    driver->setRenderTarget(ERT_FRAME_BUFFER, false, false, SColor(0,0,0,255));
    screenQuad->render();
 
    guienv->drawAll();
    driver->endScene();
 

--> it seems there is no writing to the zbuffer anymore



Is there something special to keep in mind, when using rtt? Do you have any idea?

Regards,
Tom

[mongoose7]

I'm guessing you don't clear the ZBuffer when changing render targets. There is only one Zbuffer.

[tom_gamer]

When I have

Code: Select all

driver->setRenderTarget(rtt, true, true, SColor(0,0,0,255));

the second 'true' is for clearing the zbuffer, right?

So, the zbuffer should be cleared, when the scene is drawn.

When I switch back to the frame buffer, I only draw the screen quad, which is not affected by the zbuffer.

Maybe there is a problem with the size of the rtt?

[tom_gamer]

I played around a bit...

Even when I set clearzbuffers in each line, it doesn't work.

Code: Select all

 
    driver->beginScene(true, true, backgroundColor);
    driver->clearZBuffer ();
    driver->setRenderTarget(rtt, true, true, SColor(0,0,0,255));
    driver->clearZBuffer ();
    smgr->drawAll();
    driver->clearZBuffer ();
    driver->setRenderTarget(ERT_FRAME_BUFFER, false, false, SColor(0,0,0,255));
    driver->clearZBuffer ();
    screenQuad->render();
    driver->clearZBuffer ();
 
    guienv->drawAll();
    driver->endScene();
 

I also switched from my shader to EMT_SOLID for all objects. Same result.

It's obviously related only to the rtt.

Today, I'll try to build a minimal example...

[Nadro]

Small example for reproduce this issue will be really useful.

[tom_gamer]

And finally, I found it!

It did the oldest mistake, since z buffers...

The distance between near and far plane was too big. (Near=0.5, Far=15000)
I suppose, the frame buffer calculates with 32 bits and the rtt only with 24. Very interesting.

The right solution for me is a logarithmic deph buffer. Have a look at this link: http://outerra.blogspot.de/2009/08/loga ... uffer.html
This works really great for my scene (near objects with high details and in the same scene very far objects). I put it into my shader and found no performance disadvantages.

The only drawback is, that I now have to create a shader for all objects. So, the z-value is calculated right.

Thanks to all posters...

[Nadro]

RTT depth should use the same precision as the main depth buffer (base on SIrrlichtCreationParameters::ZBufferBits parameter). For more info you can check following method:

Code: Select all

GLenum COpenGLDriver::getZBufferBits() const

COpenGLDriver.cpp at line 4710 in Irrlicht v1.8 sources.